Helicopter rotor ram jet drive



June 11, 1957 E. L. BENNETT HELICOPTER ROTOR RAM JET DRIVE Filed Sept. 29, 1955 \i.

. INVENTOR. EDWARD L, BEN/VET? BY flzg W United States PatentO HELICOPTER ROTOR RAM JET DRIVE Edward L. Bennett, Palo Alto, Calif., assignor to Hiller 'lelicopters, Palo Alto, Calif., a corporation of Caliorma Application September 29, 1953, Serial No. 382,996

2 Claims. (Cl. 170-1354) This invention relates to the starting of ram jet engines and particularly to starting such engines when they are employed on a rotating part such as a helicopter blade.

A typical form of ram jet engine with which the present invention is concerned is illustrated in the pending application for United States Letters Patent of Stanley Hiller, Jr. and Harold H. Sigler, entitled Jet Engine, filed November 20, 1951, Serial No. 257,353, now Patent No. 2,740,482. In said application, an engine is illustrated as having a somewhat tubular open ended body with a forwardly directed inlet opening and a rearwardly directed discharge opening separated by an intermediate grid or frame holder as is conventional practice. Such a ram jet engine is started after it is in forward motion at relatively high speed by spark ignition means employed to ignite a combustible fuel sprayed forwardly into the inlet portion of the tubular body.

In the application referred to above, ignition is facilitated by the provision of a trap or pocket disposed to the rear of the flame grid to entrap a mixture of fuel and air, and thus provide a relatively static mass capable of being readily ignited. A spark creating device is disposed in this trap to ignite the relatively static mass. In such engine, the fuel is sprayed in front of the flame holder by means of a nozzle; and movement of the engine at a relatively high speed is required to collect suflicient fuel in the trap for ignition of the air-fuel mixture.

It is the object of the present invention to provide means for insuring ignition or starting a ram jet engine of the kind referred to with little or no forward motion of the engine. A more specific object of the invention is to provide for positive delivery of fuel, independent of the fuel supply to the nozzle, to the pocket or trap disposed in the body of the engine for ignition therein, and provide for automatic discontinuing of said fuel delivery as the forward speed of the engine increases.

Further and more specific objects and advantages of the invention will become apparent from an understanding of the following specification wherein one form of the invention is described in detail by reference to the accompanying drawings.

In the drawings:

Fig. 1 is a central horizontal sectional view of a ram jet engine illustrated as mounted on the tip portion of a helicopter blade, and showing the application of the present invention thereto; and

Fig. 2 is an enlarged similar section of a valve mechanism illustrated in Fig. 1, and forming a part of the invention.

In Fig. 1 a ram jet engine, generally indicated at 10, is shown as secured to the outer end of a helicopter rotor blade 11 as by a bracket 12 welded or otherwise suitably secured to the engine and connected with the blade as by fastening means indicated at 13.

The construction of the helicopter blade is conventional, and the ram jet engine embodies the principle disclosed in the aforementioned application. Consequently, a detailed description of these members is unnecessary to flows directly to the nozzle.

an understanding of the present invention. However, the engine is of tubular or barrel shape, and comprises a forward air inlet opening 14 and a rear discharge outlet 15 through which exhaust. gases pass. A grid or flame holder comprising a plurality of radially disposed spokelike parts 16 is disposed somewhat forwardly of the central part of the barrel, and divides the engine into a forward diffuser section and a rear combustion section. The spokes 16 of the grid or flame holder also support a centrally disposed hub structure in the form of a nozzle seat 17 on which a conventional spray nozzle 18 is mounted.

Also supported by the spokes 16 and positioned directly behind the spray nozzle 18 is a pocket or trap 19 the function of which, as fully set forth in the co-pending application hereinabove referred to, is to entra-p and provide a relatively static mass of a certain amount of the combustible air fuel mixture which results from the forward motion of the engine through the air while fuel is being sprayed through the nozzle 18. This combustible mixture being so entrapped remains in a relatively quiescent state within the trap or pocket 19 and is, therefore, more readily ignited to effect starting of the engine than is the swiftly flowing stream of fuel and air which passes through the barrel-like body of the engine when it is in motion resulting from rotation of the wing upon which it is mounted.

In the usual operation of a ram jet engine of the kind herein shown, fuel under pressure from a suitable pump (not shown) but which is located on the ship, is directed to the spray nozzle 18 as by a conduit 20; and as the engine moves forwardly through the air, a portion of the air fuel mixture is pocketed in the trap 19 and ignited by an ignition rod or other spark creating device indicated at 21. An electrical conductor through which the rod is energized is shown at 22 as leading through the wing and is of course in communication with a battery or other source of electrical energy (not shown). This method of initiating ignition or starting a ram jet engine depends upon its forward motion through the air at a relatively high speed to create the necessary flow of fuel and air through its body for a collection of combustible mixture in the trap 19.

The present invention provides means to insure a supply of fuel to the pocket 19 While the engine is at rest or moving at relatively low speeds, and then automatically to discontinue the flow of fuel thereto when the engine has been started and is firing in forward motion. This is accomplished by a by-pass line 24 in direct communication with trap 19, and a by-pass valve generally indicated at 25 in Fig. 1 and shown in detail in Fig. 2. A main fuel line which delivers fuel from the source out to the wing tip is illustrated at 26, and valve 25 is shown as interposed between this main fuel line and the line 20 which leads to the spray nozzle.

As shown in Fig. 2, valve 25 comprises a housing body 28 with an inlet fitting 29 threaded in one end thereof and sealed by an annular gasket 29a. The inlet fitting 29 receives both the main fuel line 26 and the conduit 20 which leads to the spray nozzle, and forms communication therebetween so that upon introduction of fuel under pressure through the line 26, a portion of the fuel A valve ball 30 is disposed Within the housing 28, and is urged inwardly by a spring 31 normally to close the open end of the inlet fitting 29. Pressure of the fuel Within the line 26 will unseat the ball 30 to permit a portion of the fuel to enter the valve body and pass through a hollow fitting 32 to the bypass line 24 which is in communication therewith as shown.

Thus before the engine has started its forward motion, a portion of the fuel directed to it through the line 26 will be bypassed directly into the trap 19 and flood the same, so that ignition will be insured when the ignition rod 21 is energized. The fitting 32 within the valve provides a guide for spring 31, and is also formed with a valve seat at its end adjacent the ball 30. This valve seat is preferably provided with an annular soft or resilient seating member shown at 33. The valve is mounted adjacent the outer end of the wing as by a mounting bracket 34; and a suitable gasket 35 is interposed between the inside of this bracket and a groove in the end of the fitting 29 to insure against leakage.

The position of the valve is such that upon forward movement of the engine at substantial speed sufiicient to cause self-firing.of the engine, when it is started, inertia will cause the ball to seat upon the member 33, and prevent the passage of fuel through the bypass line. In the present case, the valve is mounted so that the movement of ball 30 is in the same general direction as the longi tudinal axis of the wing so that upon rotation of the wing, the ball tends to move outwardly and in opposition to the force exerted by the spring 31. The weight of the ball 30 and the tension of the spring 31 are such that the pressure of fuel in the line 26 will unseat the ball from its innermost seat on the fitting 29 to permit bypassing of fuel when the wing and engine are at rest or moving at relatively low speed.

However when ignition of the bypassed fuel in the trap 19 occurs, the engine is moved forwardly at increasing speed as the rotor is driven during starting; such movement being in a circular path defined by the rotary motion of the tip of the rotor blade. When suffioient forward speed is reached to insure trapping of sufiicient fuel in trap 19 for maintaining ignition, the centrifugal action caused by this motion causes the ball 30 to move outwardly against the action of spring 31, and to seat against its outer seat 33 thus closing the passage through the hollow fitting 32 and bypass line 24 so that the flow of bypass fuel to the trap 19 is discontinued, and fuel flows only to nozzle 18. When the engine moves through the air at a sufficient speed so that it is self-firing, it is understood that the ignition is turned off.

Trap 19 is illustrated herein as semi-spherical but it may be otherwise shaped if desired. It is also preferable that the trap have a plurality of small perforations as shown at 35 to prevent the accumulation therein of an excessive quantity of liquid fuel. As in the device of the aforementioned application, the front end of trap 19 communicates with open spaces between spokes 16, to allow pocketing of the air-fuel mixture in the trap.

I claim:

1. The combination with a blade of a helicopter, of a ram jet engine supported by said blade and including a fuel nozzle and a trap for combustible fluids behind the nozzle, ignition means in the trap, a fuel line to the nozzle, a bypass in said line to the trap, a valve in said bypass including a seat and a closure, and a spring urging the closure away from the seat and inwardly relative to the blade, whereby uponstarting of the engine and rotation of the blade the closure will be centrifugally urged against the seat.

2. The combination with a blade of a helicopter, of a ram jet engine supported by said blade and including fuel supply means and a shielded section for combustible fluids, ignition means in said shielded section, a fuel line to the fuel supply means, a by-pass in said line to the shielded section, a valve in said by-pass including a seat and a closure, and a spring urging the closure away from the seat and inwardly relative to the blade, whereby upon starting of the engine and rotation of the blade the closure will be centrifugally urged against the seat.

Haworth et al .H Feb. 27, 1951 Allen Apr. 5, 1955 

